The Oregon State football team's passing game ranked No. 20 in the nation and averaged 307.1 yards a game last season.

Many of those yards came from the receiving duo of Markus Wheaton and Brandin Cooks. They combined for 184.2 yards a game, and Wheaton contributed 95.7.

Wheaton moved on and is giving the NFL a try as a probable draft pick at the end of the month.

That leaves a huge offensive void for the Beavers because he was also a rushing threat on the fly sweep with 10.9 rushing yards a game and two touchdowns.

"There's a lot of production to fill with Markus Wheaton gone," coach Mike Riley said. "Someone has to emerge, and more likely two receivers."

Success for the Beavers came from the proven ability of Wheaton and the advanced upstart skills of Cooks. Whoever opponents double-teamed the other could shake one-on-one coverage.

Cooks is now the proven talent going into his junior season, but needs someone to complement him the way he did with Wheaton.

Richard Mullaney was a play-maker in practice last season and transferred that into games for a while with 13 receptions for 156 yards and a touchdown in nine games. He briefly played well in place of Wheaton, who suffered a concussion against Washington.

Mullaney, a sophomore, would have been atop the depth chart this spring if healthy. A partially torn rotator cuff kept him out of four games and he's recovering from offseason surgery this spring. He was hurt during a practice when he dove for a ball and landed on his shoulder.

For now, Mullaney will watch others battle it out this spring and hopes he recovers enough to train in the summer to stake his claim at the starting split end job in the fall.

"He has shown us he can play," receivers coach Brent Brennan said. "Richard Mullaney is someone we think highly of when he gets well. It just depends how he plays against those guys in the fall. It's who plays well over the next five months."

With Mullaney out, that leaves Obum Gwacham first on the spring depth chart. He's an athletic junior who hasn't been able to stick at either split end or slot receiver.

Malik Gilmore, a 6-foot-3, 214-pounder, impressed the coaches on the scout team during his redshirt season and is trying show he now knows OSU's system.

"It's a great time for Malik and a great time for Obum Gwacham to step up and move forward," Riley said. "It's too bad Mullaney is not in the mix. It would be fun to have him out there in the spring but he will be in the fall."

Quarterback Sean Mannion will miss throwing to Wheaton, but he feels comfortable with the players coming up the ranks.

"The example he set here on and off the field is really reflected in the guys still here," Mannion said. "They took his work ethic and determination to improve. We have a lot of young guys ready to step in."

Mannion enjoyed the first two days of spring practice this week working with younger players such as Gilmore because he only heard about what he was doing on the scout team.

"That's exciting to see all the young guys, and they are great players," Mannion said. "Malik is an exciting player. He's big and athletic. I can't wait to see him develop."

Gwacham is also a standout high jumper with the track team, but he decided to redshirt this season in track so he can concentrate on being a receiver. His inconsistencies in practice have held him back.

"They know Markus is gone and they are fighting their butts off to be that guy," Brennan said. "That's going to put a lot of pressure on both of them on a daily basis. The competition of that position is going to be a lot of fun going through the fall."

While there's a position battle for the split end position, the Beavers have the ability to spread the ball around to a deep group of receivers.

Micah Hatfield worked behind Wheaton and Cooks last season. He was productive as a backup with nine receptions, two for touchdowns.

Kevin Cummings began to emerge from the starting slot receiver position with 18 receptions with an average of 11.6 yards a catch and a touchdown.

"There's some optimism there with the guys in the program, and it should be interesting," Riley said. "Cummings, Cooks and Hatfield will be even better this season."

The Beavers also signed four three-star receivers in Victor Bolden, Hunter Jarmon, Jordan Villamin and Walter Jones. They'll get a good look in the fall to see if they are ready to play as true freshman.

Riley's not ruling out his incoming freshman to make an impact, but he would like to redshirt them and go with what he has this spring.

"There are names there, but I don't want to be overly optimistic of freshman," Riley said. "We have four good ones coming in. Three of them have speed and Villamin is big."